The Association Between Melasma and Thyroid Dysfunction: A Case-Control Study

Background: Melasma is a common pigmentary disorder predominantly affecting women. Thyroid hormones influence skin homeostasis and melanocyte activity, suggesting a possible link with melasma. Objective: To investigate the relationship between thyroid hormone levels and melasma in women. Methods: A case-control study was conducted with 100 women aged 18–45 years, including 50 patients with melasma and 50 healthy controls. Free triiodothyronine (T3), free thyroxine (T4), and thyroid-stimulating hormone (TSH) levels in the blood were evaluated in both the clinic and the lab. Results: Women with melasma were significantly older than controls (p=0.001). Compared to controls, melasma patients had lower median free T3 [3.0 (2.6–3.6) vs. 3.3 (3.2–3.5); p=0.02] and free T4 [1.3 (1.1–1.5) vs. 1.4 (1.3–1.4); p=0.001] and higher TSH levels [3.7 (2.8–4.2) vs. 2.2 (1.9–2.5); p=0.001]. These differences remained significant after adjusting for age. Overt thyroid dysfunction was uncommon and not significantly different between groups (p=0.35). Conclusions: Subclinical alterations in thyroid hormones may be associated with melasma in women, independent of age, although causation cannot be established.